Posting comments gets stuck at /CommentingController/CommentsForm

I have the blog, comments and widgets modules installed. Comments were working, but recently I whenever I post a comment I get redirected to a blank page at /CommentingController/CommentsForm. Pretty sure I didn't change anything with the comments or blog modules. Anyone else have this problem?

Check your PHP error log for any error messages. Does the comment get saved? The normal behaviour is you will be redirected to CommentingController/CommentsForm but that will take you back to your last page after it has finished processing.